Method of finishing gears



April- 20, 1943. w. A. WITHAM METHOD OF FINISHING GEARS Original FiledJan. 28, 1956 4 Sheets-Sheet 1 //VVE'NTOR wTAlw/THAM v ATTtRjEY April20, 1943. w. A. WITHAM METHOD OF FINISHING GEARS Original Filed Jan. 28,1936 4 Sheets-Sheet 2 lnvcntor W. A. W/TH/QM ttorncg April 20, 1943. w.A. WITHAM 2,317,161

METHOD OF FINISHING GEARS Original Filed Jan. 28, 1936 4 Sheets-Sheet 3%19 v fl zo WA W/THHM g ATTORNgY April 20, 1943. w, wlTHAM 2,317,161

METHOD OF FINISHING GEARS Original Filed Jan. 28, 1936 4 Sheets-Sheet 4ATTORNE Patented Apr. 20, 1943 2,317,161 METHOD or FINISHING GEARSWinfred A. Witham, East Rochester, N. Y., as-

signor to Gleason Works, Rochester, N. Y., a corporation of New YorkOriginal application January 28, 1936, Serial No.

61,237, now Patent No. 2,295,148, dated September 8, 1942. Divided andthis application October 9, 1940, Serial No. 360,445

16 Claims.

The present invention relates to tools for and to methods of finishinggears and particularly to tools for and to methods of shaving spiralbevel and hypoid gears. The present application is a division of myco-pending application Serial No. 61,237, filed January 28, 1936, nowPatent No. 2,295,148, of Sept. 8, 1942. It covers specifically the gearfinishing process.

Efforts to shave bevel gears have heretofore been based upon theassumption that it is necessary to have some relative lengthwise slidingaction between the tooth surfaces of the gear being shaved and thecutting edges of the shaving tools in order to have the cutting edges ofthe tool take shaving cuts. For this reason, it has been further assumedthat the cutting edges of the shaving tools should extend up and downthe profile of the teeth of the tool in a direction approximately atright angles to the direction of relative sliding. For shaving spiralbevel gears, therefore, the tools heretofore used have been made ofhypoid gear form and have been generated to mesh in offset relation withthe gear to be shaved so that when tool and gear were rotated in mesh,the relative sliding action would be obtained between the tool and gearwhich is characteristic of the mesh of a pair of hypoid gears. Theproduction of a hypoid gear conjugate to a given spiral bevel gear is,however, a complicated kinematical problem and long processes ofdevelopment have been required to produce satisfactory forms of hypoidshaving tools.

As a result, the shaving of spiral bevel gears by such processes as haveheretofore been proposed have not reached a commercial stage.

One object of the present invention is to provide a process for shavinggears and particularly for shaving bevel gears which will not dependupon or require relative lengthwise sliding between the tooth surfacesof the gear and the cutting edges of the shaving tool in order to eifectthe shaving action.

A further object of the invention is to provide a process for shavingspur, bevel and hypoid gears in which the shaving gear or tool and thegear to be shaved may be rotated together on relatively fixed centers.

Another object of the invention is to provide a process for shavinggears which can be performed on apparatus of a relatively simple typesuch as is now commonly used for the testing or burnishing of gears.

A further object of the invention is to provide a gear shaving processwhich will permit of the use of a shaving tool which will very closelyapproximate the form of a mate of the gear to be shaved so that thedevelopment of costly, special forms of shaving tools, such asheretofore required, may be eliminated.

A still further object of the invention is to provide a more efficientprocess for shaving gears, particularly bevel and hypoid gears.

Other objects of the invention will be apparent hereinafter from thespecification and from the recital of the appended claims.

The present invention is based upon the discovery that, if a shavingtool is used which has its cutting edges inclined at a suitablerelatively small angle to the lines of contact between the teeth of theshaving tool and the teeth of the gear to be shaved, it is not necessaryto effect any relative lengthwise movement between the teeth of tool andgear, but that satisfactory shaving action may be achieved by simplyrotating the tool and gear together. Where the cutting edges of the toolare properly inclined to the lines of contact, the shearing cut will beachieved that is required to produce efficient, smooth cutting action.Hence it is no longer necessary to employ a tool of hypoid gear form toshave a bevel gear. A bevel gear may be shaved with a tool of bevel gearform which meshes with the gear with its axis intersecting the axis ofthe gear. Further, a hypoid pinion may be shaved with a tool of taperedgear form whose axis has the same offset from the axis of the pinion asthere is between the pinion and its mate hypoid gear when the pinion isin mesh with its mate- When a pair of spiral bevel gears are rotated inmesh, the lines of contact between the mating tooth surfaces of thegears extend diagonally across the tooth surfaces from one end of theteeth to the other. Hence for shaving spiral bevel gears by the processof the present inven tion, a tool of spiral bevel gear form is usedwhich has its cutting edges extending parallel to or substantiallyparallel to the root surface of its teeth. Such cutting edges aresuitably inclined to the lines of contact between the tool and the gearto be shaved, and when gear and tool are run in mesh a clean, shearingcut is obtained. For shaving hypoid pinions, the tool used may be ofhypoid gear form but it may also have its cutting edges extendingparallel to its root lines since, as in the case of spiral bevels, thelines of contact between a pair of hypoid gears extend diagonally acrossthe tooth surfaces from one end to the other.

Since the lines of contact between a pair of spiral bevel or a pair ofhypoid gears extend in different directions on the two sides of the gearteeth, it may be desirable in some instances to have the cutting edgeson one side of the teeth I of the shaving tool extend in a somewhatdifferent direction from the cutting edges on the other side of theteeth. This is not necessary in all cases, however, and other expedientsmay be adopted to compensate for this difference in inclination of thelines of contact as will be described more fully hereinafter,

Ordinarily tools are used whose tooth surfaces are of straight profile,that is, the tools are made by grooving the sides of the teeth ofnon-genera ated gears. Such a tool is easy to grind and to resharpen.The whole profile of a tooth can be ground simultaneously.

For shaving a spiral bevel gear or pinion, the shaving tool is meshedwith the gear to be shaved with its axis intersecting the axis of thegear to be shaved and the tool and gear are rotated in mesh while beingforced together under spring pressure or while a positive depthwise feedmovement is effected between them to shave the full height of the teeth.For shaving hypoid gears, the tool may be meshed with the bear to beshaved with the same offset between the axis of tool and gear as is usedbetween the gear, which is being shaved, and its mate when the pair arein mesh, and tool and gear are rotated together while relative depthwisemovement is effected under spring load or positively.

The tool employed may have its teeth shaped to have full lengthwisecontact with the teeth of the gear to be shaved or to have only partiallengthwise contact. In the former case, no other motions are requiredfor finishing the gears other than rotation and depthwise movement. Inthe latter case, an additional movement lengthwise of the teeth of thework is required but merely to effect shaving along the whole length ofthe teeth.

'Where rapid cutting action is desired, a shaving tool may be employedwhich has teeth not only grooved but also gashed transversely. With sucha tool, the amount of pressure required to effect the shaving operationis materially reduced.

The invention is not restricted to shaving of spiral bevel and hypoidgears, but its principles may be applied to the shaving of other formsof gears also, such as spur gears.

In the drawings:

Fig. 1 is a fragmentary axial section and Fig. 2

a fragmentary plan view of a tool such as may be employed for shavingspiral bevel gears accordin to the method of the present invention.

Fig. 3 is a fragmentary perspective view of this tool;

Fig. 4 is a fragmentary axial section and Fig, 5 a fragmentary plan viewof a modified form of tool such as may be employed in practicing thepresent invention;

Figs. 6 and 7 are fragmentary axial sectional views of a tool, such asshown in Figs. 1 to 3 inclusive, and showing the relationship betweenthe cutting edges of the drive side of the teeth of such a tool and thelines of contact between the tool and the gear, which is to be shaved,when the tool and gear are rotated in mesh;

. Figs. 8 and 9 are corresponding fragmentary axial sectional views ofthe tool illustrating diagrammatically the relationship between thelines of contact and the cutting edges on the coast side of the teeth ofthe tool when the cutting edges are arranged in the same way as on thedrive side of the teeth, that is, parallel to the root lines of thetool;

Fig. 10 is a fragmentary axial sectional view showing diagrammaticallythe relationship between the lines of contact and the cutting edges onthe coast side of a tooth of a slightly modified form of the tool;

Fig. 11 is a fragmentary axial sectional view of an automotive drivegear and showing diagrammatically a typical tooth bearing between such agear and its mate when the pair are in mesh;

Fig. 12 is a fragmentary axial sectional view showing diagrammaticallyby way of contrast the tooth bearing between a tool gear and a pinion,which is te be shaved, when a tool gear is used whose teeth have fulllengthwise contact with the teeth of the pinion;

Fig. 13 is a corresponding fragmentary axial sectional view showing thetooth bearing between the tool gear and the pinion being shaved when atool gear is employed whose teeth have localized contact with the teethof the pinion;

Fig. 14 is a View illustrating diagrammatically the method of shaving abevel pinion with a tool gear constructed as illustrated in Fig. 12;

Fig. 15 is a corresponding diagrammatic view illustrating the method ofshaving a hypoid pinion when a tool gear is used of the constructionillustrated diagrammatically in Fig. 12;

Fig. 16 is a view illustrating diagrammatically the method of shaving abevel pinion when a tool gear, such as is illustrated in Fig. 13, isemployed as the shaving tool;

Figs. 17 and 18 are a fragmentary axial section and a plan view,respectively, showing a tool gear, such as may be employed for shavingskew bevel gears according to the present invention, and illustratingdiagrammatically, on the drive side of the teeth, the preferredrelationship between the cutting edges of such a tool and the lines ofcontact of the tool with the gear to be shaved;

Figs, 19 and 20 are a fragmentary axial section and a plan view of ashaving tool for shaving straight bevel gears according to the processof the present invention, and illustrating the preferred relationship,on the drive side of the teeth between the cutting edges of such a tooland the lines of contact;

Fig. 21 is a fragmentary perspective view of a tooth of a modified formof shaving tool, such as may be employed for shaving spiral bevelpinions according to this invention;

Fig. 22 is .a fragmentary perspective view of a tooth of a tool forshaving hypoid pinions according to the process of the presentinvention; and

Figs. 23 and 24 are diagrammatic views illustrating the principles whichshould be followed in determining the relationship between the groovesand gashes of a tool, such as shown in Fig. 4, in order to have thecuttingedges of such a tool shave the whole of the tooth surface of apinion.

When a pair of spiral bevel gears are rotated in mesh, the mating toothsurfaces of the pair contact, as already stated, along lines which arecurved and which extend diagonally across the tooth surfaces of thegear. For the drive sides of the teeth, these lines extend in onedirection and for the coast side of the teeth, they extend in theopposite direction. Thus, as shown in Fig. 6, the line of contact of thedrive side of a tooth 50 of a spiral bevel gear 52 with the toothsurface of a mating pinion will, for one instant of mesh, extend alongthe curved line 54. For the coast side 55 of this same tooth of the gear52, the line of contact, at the same instant, will be a curved line 56,such as shown in Fig. 8. As the gear and its mate roll together, theselines of contact will move across the tooth surface of the gear from topto bottom thereof. Thus, other positions of the lines of contact forother positions of mesh of gear and pinion are indicated at 54' and 54"in Fig. 6 and at 56 and 56" in Fi 8.

Now to obtain satisfactory, smooth cutting action, where relativesliding is not to be relied on, I have found that the cutting edges ofthe shaving tool must be properly inclined to these lines of contact.Thus on a spiral bevel shaving gear, I have found that the cutting edgesmay have the same inclination to the lines of contact as the root linesof the teeth have to the lines of contact, and that correct cuttingaction may then be obtained without effecting any relative slidingaction between the teeth of the tool and of the work. It will be noted,however, from Figs. 6 and 8 that the of contact have diiferentinclinations to the root lines of the teeth for opposite sides of theteeth. Thus for the drive side of the teeth, as shown in Fig. 6, thelines of contact 54 are inclined at some angle A to the pitch line 58 ofthe gear tooth and at an angle A-6 to the root line 59 of the teethwhere a is the dedendum angle. For the coast side of the teeth, however,as will be seen from Fig. 8, while the line of contact 56 has the sameinclination A to the pitch surface 58 as for the drive side of theteeth, the line of contact 56 is inclined to the root line 59 at anangle A+6.

For most automotive jobs, I have found that this difference ininclination of the lines of contact to the root line on opposite sidesof the spiral bevel gear teeth is not great and can be disregarded andthat, when cutting edges 6!] and BI, respectively, are provided on theopposite sides of the teeth of a spiral bevel shaving gear 52, which areparallel to the root lines of the teeth of such a gear, a satisfactoryshearing, cutting action is obtained. The angle between the cuttingedges and the lines of contact may vary. I have found the angle may varyfrom 3 to or more. Of course, when the cutting edges are parallel to theroot line on both sides of the teeth of the shaving tool, it verymaterially simplifies the production of the tool. The only noticeableeifect in use of such a shaving tool is that in some instances theshaving action may take place slightly faster on the coast side than onthe drive side of the teeth.

In those instances where it is desired that the shaving action proceedat the same rate on both sides of the teeth, a shaving gear may beemployed which has cutting edges on the coast side that have the sameinclination to the lines of contact for that side of the teeth as thecutting edges on the drive side of the teeth have to the lines ofcontact for the latter side of the teeth. The coast side of a tooth ofsuch a tool is illustrated in Fig. 10. Here the cutting edges 65 on thecoast side 56 of the tooth of a shaving gear El are shown inclined tothe root line 68 of this gear at such an angle that the cutting edgesmake an angle A-6 with the lines of contact 10 for this side of theteeth. This angle A-& is equal to the angle of inclination (A-6) of thecutting edges on the drive side of the teeth to the lines of contact 54for that side of the teeth.

The cutting edges of the tool may be formed by taking a gear which willmesh with the gear to be shaved and grooving the side surfaces of theteeth of this gear. Thus, in Figs. 1 to 3 inclusive, I have shown a toolfor shaving spiral bevel pinions. The tool itself is denoted at 49. Itis formed from a standard spiral bevel gear of non-generated form havingside tooth surfaces that are of straight profile and are conicalsurfaces of revolution. Grooves 42 are formed longitudinally in thesides of the teeth of the gear. These grooves are made parallel to theroot lines of the teeth on both sides of the teeth. The lands 43 betweenthe grooves lie in the original tooth surfaces oi the gear and the landsare, therefore, of straight profile and lie in conical surfaces ofrevolution.

Preferably the grooves and lands are displaced with reference to oneanother on successive teeth of the tool so that the cutting edges formedby the grooves and lands will be displaced with reference to one anotheron successive teeth. In this way the effect of a great number of cuttingedges will be obtained and a smoother surface will be secured.Preferably, the grooves and lands are so arranged on the correspondingsides of successive teeth as to be displaced spirally with referencewith one another around the teeth of the gear. Such an arrangement isshown in Fig. 3 where the cutting edges 44, 45 and 46 of successiveteeth of the tool 4 2 are shown arranged on a spiral 41. The lead of thespiral and the number of the spirals around the gear are determined bythe form and character of the shaving gear and also by the quality offinish desired on the pinion to be shaved.

Up to this point, only tools for the shaving of spiral bevel gears andpinions have been specifically described. The invention is applicable,however, to the shaving of all types of gears, and the relationship,which has been discovered between the directions of the lines of contactand the cutting edges, must be observed for a shaving gear of any formif smooth, efficient cutting action is to be obtained Without anyrelative sliding movement between the tool and the gear to be shaved.

For skew bevel gears, the lines of contact between the mating toothsurfaces of a pair of gears are straight but inclined to the root linesof the teeth on opposite sides of the teeth at the same angle as forspiral bevel gears of the same size. In Figs. 17 and 18, Bil denotes atool such as may be employed in the process of the present invention forshaving skew bevel gears. The teeth this tool have tooth surfacesgrooved, as inclidated at 82 in a direction parallel to the root lines83 of the teeth. This tool gear is of the same size as the spiral beveltool gear 52 shown in Fig. 7. Hence while its lines of contact E i arestraight, they will have the same inclination A-a to the root lines 83of the teeth as have the lines of contact 54 of the spiral bevel gear52. The drive side only of the skew bevel tool gear is shown in Fig. 17.The grooves in the coast side of the teeth of this gear may also be madeparallel to the root line of the teeth similar to the tool shown in Fig.9, or they may be inclined to the root line so that the cutting edgeshave the same inclination to the lines of contact on the coast side ofthe teeth as on the drive side, corresponding therefore to the spiralbevel gear tool shown in Fig. 10..

For shaving straight bevel gears, a tool will be used such as shown inFigs. 19 and 20. The lines of contact between the teeth of such a tooland the tooth surfaces of a straight bevel gear or pinion being shavedare straight lines which run to the gear apex of the tool. One of suchlines is denoted at 94 in Fig. 19. To obtain. efficient, smooth cuttingaction, the cutting edges of the tool gear 60 should be inclined to thelines of contact 94 at approximately the same angle as between thecutting edges and lines of contact in the case of the spiral bevel toolgears al ready described. This means that the teeth of the shaving gear90 should be grooved substantially as shown at 62 in Fig. 19 so as toobtain cutting edges 95 which are inclined to the lines of contact 64 atsubstantially an angle A6 equal to the angle A-t previously referred to.

Since straight bevel gears contact along the whole length of their toothsurfaces simultaneously and since portions of the tooth surfaces of astraight bevel shaving tool are necessarily cut away to provide thecutting edges, it is desirable that where a straight bevel shaving gearis emplayed, some means be provided to maintain correct timed relationof the tool and gear to be shaved as they rotate together. Such meansmay comprise a train of gearing, positively driving the tool and gearspindle in a timed relation corresponding to the ratio of a number ofteeth of the tool gear and the gear to be shaved.

Fig. 22 shows a form of tool gear such a may be employed for shavinghypoid pinions by the process of the present invention. It is desirablein the case of such a. tool to have the cutting edges extend parallel tothe root lines of its teeth. To obtain the desired direction of thecuttin edges, it is necessary, because of the offset relation of hypoidgears, to reduce the pressure angle on the drive side of the teeth ofthe hypoid shaving gear and to increase it on the coast side, ascompared with the pressure angles used on the spiral bevel shaving gear.Thus, as shown in Fig. 22, the pressure angle a of the drive side I00 ofthe tooth I6! of the hypoid shaving gear is considerably less than thepressure angle a of the coast side I02 of the tooth. This contrasts withthe construction of the spiral bevel shaving gear shown in Fig. 21. Inthe case of the tooth shown in Fig. 21, the pressure angles a" of thetwo sides of the tooth I05 are equal, although the included anglebetween opposite sides of the tooth may be the same as the includedangle between opposite sides of the tooth I0l of the gear illus-- tratedin Fig. 22.

When a hypoid shaving tool constructed as shown in Fig. 22 is employed,the lines of contact 564 for the drive side of the teeth extendsubstantially in the same direction as the lines of contact 54 of thespiral bevel shaving gear shown in Fig. '7, and the lines of contact onthe coast side of the teeth will extend substantially in the samedirection as the lines of contact 56 of the coast side of this samespiral bevel shaving gear. Hence both sides of the teeth of a tool gear.such as shown in Fig. 22, may be formed with grooves which extendparallel to the root lines of the teeth, and such a tool gear will havesubstantially the same action when shaving a hypoid pinion as the spiralbevel shaving tool shown in Figs. 7 and 9 will have when shaving aspiral bevel pinion.

The grooves may be cut in the shaving tools in any desired manner. Whilein the drawings, these grooves extend along straight lines, it ispossible to have them extend also along curved lines. The grooves may beof any desired shape in cross section, they may have theirsides'perpendicular to the sides of the teeth, or parallel to the toplands of the teeth, or they may. have any other suitable direction asdescribed more particularly in my parent application No. 61,237.

Where quite rapid cutting action is desired, shaving tools may beemployed which are crossgashed in addition to being grooved, as shown inFigs. 4 and 5. Here a shaving tool I25 is illustrated which has itsteeth I3I grooved, as indicated at I26, to provide longitudinal cuttingedges parallel to the root lines of the teeth. This shaving tool alsohas its teeth gashed transversely, as indicated at I21, to provideprofile cutting edges I28 and I29. The gashes I21 extend entirelythrough the teeth and are, in the form shown, V- shaped so that thecutting edges I28 and I29 are slightly inclined to the pitch surface ofthe tool. The cross gashes may be arranged on a spiral as indicated atI33 in Fig. 5, or on circular arcs or have any other direction asdesired. They may be normal to the teeth or extend at any desired anglerelative thereto. 7

Where the teeth of the shaving tools are both grooved and gashed, meredisplacement of the grooves on different teeth is not sufficient toinsure com lete coverage and complete finishing of the tooth surfaces ofthe gear and pinion being shaved. The grooves must be displacedaccording to a definite law as will now be described.

Fig. 23 is a more or less diagrammatic ide elevation of a tooth of ashaving gear. This tooth provided with longitudinal grooves I60extending parallel to the root line I63 of the tooth. Between thegrooves I60 are lands I61 whose side edges I62 form the longitudinalcutting edges of the tool. The tooth is also gashed-transversely byV-shaped grooves I64 which form profile cutting edges I65 and I66.

In the tool illustrated in Fig. 23, the grooves I66 and lands I 6| arearranged on a spiral which has a lead equal to the pitch of the groovesso that the grooves are displaced on successive teeth of the tool adistance equal to the pitch of the grooves divided by the number ofteethof the tool. With this construction, the bottom right hand cornerof the lands I6I of the tool lie on a helical line I61 and thecorresponding corners of the lands next highest on the profile of theteethlie in a helical line I68. Diagonally opposite corners of these twoseries of lands lie on the lines I69 and I10, respectively. From Fig. 23it will be noted that the lines I69 and I68 diverge toward the righthand or large end of the tooth. In other words, there is a space betweenthe lines I68, I69 where there are no cutting edges and hence wherethere would be no shaving action. If a shaving tool were used, then,having grooves and gashes arranged inthe manner shown in Fig. 23, thegear being operated upon would not be completely shaved.

If the tool has its grooves arranged, however, as shown in Fig. 24, theshaving action will be complete. Here the lead of the spirals of thegrooves and lands is equal to twice the pitch of the grooves. Thus thelower right hand corners of one series of lands I12 are arranged on ahelix I13 and the corresponding corners of the next higher series oflands lie in a helix I16,- The diagonally opposite left hand corners ofthese two series of lands lie in helices I16 and. I11, respectively. Itwill be noted that the helix I15 completely overlaps thehelix I16.Hence, the cutting edges of the shaving tool will completely cover thetooth surfaces of the gear to be shaved and completely shave the same.

Complete coverage of the tooth surfaces of the gear can be obtained,then, by displacing the gashes from tooth to tooth on the shaving gear adistance equal to the pitch of the gashes divided by the number of teethin the gear, and by displacing the grooves a distance equal to twice thepitch of the grooves divided by the number of teeth in the gear, or,still more broadly, by displacing the grooves from tooth to tooth adistance equal to a multiple of the pitch of the grooves divided by thenumber of teeth in the shaving tool.

In a tool to be used according to the process of the present invention,grooves and lands may be of equal width and the same size grooves andlands may be used on both sides of the teeth, or grooves and lands maybe of different widths and different size grooves may be used onopposite sides of the teeth. The narrower the lands, the smaller theunit pressure required to shave and the faster the shaving action undera given pressure. Where the shaving action is too rapid on the coastside of the teeth as compared with the drive side, the action may beequalized by making the lands wider on the coast side of the teeth thanon the drive side. Such construction is illustrated in Fig. 21. Here thelands I80 for the coast side of the tooth I of the shaving tool arewider than the lands I82 of the drive side of the tooth.

Ordinarily the tool gear used will have teeth of greater chordalthickness than the teeth of the mate of the gear which is being shavedso that the tool and the gear to be shaved may mesh without any backlashand the tool may cut simultaneously on both sides of the tooth spaces ofthe gear being shaved.

The radii of curvature of the mating tooth surfaces of a pair ofautomotive drive gears are usually selected so that they mismatch and sothat when the pair of gears are meshed in correct position withoutload," the bearing or tooth contact will be concentrated at the smallend of the gear teeth as indicated by the shaded portion ISIl of thetooth Iii! shown in Fig. 11.

For shaving spiral bevel or hypoid gears according to the process of thepresent invention, shaving tools are employed whose tooth surfaces arecurved longitudinally either to match the tooth surfaces of the gear tobe shaved along the whole length of such tooth surfaces, or the toothsurfaces of the shaving gear are so curved longitudinally that the teethof the shaving gear and the tooth surfaces of the gear to be shaved willhave localized contact at the center of the tooth surfaces.

Fig. 12 illustrates the tooth contact of a shaving gear of the firsttype. Here the shaving gear I93 has tooth surfaces longitudinally curvedin such way that their radii match exactly the radii of the mating toothsurfaces of the gear to be shaved. Hence the teeth of the shaving gearI93 will have full length bearing contact, as indicated by the shadedsurface I92, with the tooth surfaces of the gear to be shaved.

Fig. 13 illustrates diagrammatically the construction of a shavin gearof the second type described. Her the shaving gear has tooth surfaces socurved longitudinally as to be tangent to the meshin tooth surfaces ofthe gear to be shaved at points midway the length of the tooth surfaces.7 Hence the tooth hearing, as indicated in shaded lines at I95, will belocalized midway the length of the tooth surface.

When a shaving tool, such as illustrated in Fig. 12, is employed forshaving spiral bevel or hypoid gears, the shaving gear and the gear tobe shaved are run together on fixed centers Without any motion otherthan a feed motion in the direction of tooth depth. Thus, as shown inFig. 14, when a bevel pinion 269 is to be shaved with a bevel shavinggear 28I constructed as shown in Fig 12, the pinion and shaving toolwill be meshed like an ordinary pair of bevel gears with the axis 292 ofthe pinion intersecting the axis 2i33 of the shaving gear, and thepinion and shaving gear will be rotated together on their axes while arelative depthwise feed movement is produced between them, Either gearor pinion may act as the driver.

Likewise when a hypoid pinion 265 is to be shaved with a hypoid shavinggear 286 whose teeth are cut to have a full length bearing with thetooth surfaces of the pinion, the pinion and gear will be meshed onfixed centers with the aXis 291 offset from the axis 288 of the shavingtool a distance equal to the offset between the axis of the pinion andits mate gear when in mesh. For shaving the pinion 205, the pinion 20 5and the tool gear 296 are rotated in mesh upon their respective axeswhile a simple feed movement depthwise of the teeth is produced to shavethe teeth of the pinion for their full height.

When a tool gear is employed, whether it be a bevel or a hypoid toolgear, which is constructed, as shown in Fig. 13, tohave a localizedtooth bearing with the gear to be shaved, then it is necessary toproduce a motion lengthwise of the teeth of the gear to be shaved, inaddition to the rotary motions of tool and gear, in order to shave theteeth of the gear for its full length. For this purpose the shavingoperation may be effected on a machine such as described in a patent toSlade, No. 1,796,484 of March 17, 1931. The method of operation of thismachine is illustrated diagrammatically in Fig. 26. 2 I I) denotes thehypoid pinion to be shaved and 2 is the shaving tool. The shaving gear 2is secured to a spindle, which is mounted eccentrically in anoscillatable carrier 2 I2, with the axis 2l3 of the shaving gear offsetfrom the axis 2M of the carrier. The pinion may act as the driver, and,as the pinion and shaving gear rotate in mesh, the carrier 2I2 isoscillated to move the tooth bearing or contact of the shaving gear fromone end of the pinion teeth to the other, thereby shaving the wholelength of the tooth surfaces of the pinion. A relative depthwise feedmovement may be produced manually between the shaving gear and pinionduring rotation, or the tool and pinion may be forced into depth underspring pressure.

For the shaving of spur gears according to this invention, a tool willbe employed which has its cutting edges extending longitudinally of itsteeth but inclined to the pitch and root lines of the teeth inaccordance with the principles above set forth. For the shaving ofhelical gears, the tool used should have its cutting edges extendingparallel to the root and pitch lines of its teeth, for the teeth ofhelical gears contact along lines inclined to the pitch and root linesofthe teeth. With such tools, spur and helical gears, respectively, may beshaved by simple rotation of tool and work together.

While several different embodiments of the inventionhave beenillustrated and described, the

invention is capable of still further modification, and this applicationis intended to cover any adaptations, uses, or embodiments of theinvention, following, in general, the principles of the invention andincluding such departures from the present disclosure as come withinknown or customary practice in the gear art and as may be applied to theessential features hereinbefore set forth and as fall Within the scopeof the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

1. The method of finishing one member of a pair of tapered gears whichcomprises employing a tool of tapered gear form that has the oppositesides of its teeth grooved longitudinally to provide cutting edges whichextend longitudinally of the teeth, all of which are inclined to thetops of its teeth on both sides of its teeth and to the lines of contactbetween said teeth and the tooth surfaces of the gear to be shaved whenthe tool and gear are rotated in mesh, positioning the tool inengagement with the gear so that the tool and gear axes have the samerelative positions as the axes of the gear being finished and of itsmate when the pair are in mesh, and rotating the tool in engagement withthe gear While effecting a relative depthwise movement between the tooland gear to finish the teeth of the gear to the desired depth.

2. The method of finishing one member of a pair of longitudinally curvedtooth tapered gears which comprises employing a tool of tapered gearform that has longitudinally curved teeth and that has the sides of itsteeth grooved longitudinally to provide cutting edges which extendlongitudinally of the teeth parallel to the root lines of the teeth onboth sides of the teeth, positioning the tool in engagement with thegear so that the tool and gear axes have the same relative positions asthe axes of the gear being finished and of its mate when the pair are inmesh, and rotating the tool in engagement with the gear while efiectinga relative depthwise movement between the tool and gear to finish theteeth of the gear to the desired depth.

3. The method of finishing one member of a pair of longitudinally curvedtooth tapered gears which comprises employing a tool of tapered gearform that has longitudinally curved teeth and has cutting edges formedon the sides of its teeth by alternate grooves and lands that extendlongitudinally of the teeth parallel. to the root lines of the teeth,and which has wider lands on one side of its teeth than on the other,positioning the tool in engagement with the gear so that the tool andgear axes have'the same relative positions as the axes of the gear beingfinished and of its mate when the pair are in mesh, and rotating saidtool in engagement with the gear while effecting a relative depthwisemovement between the tool and gear to finish the teeth of the gear tothe desired depth.

4. The method of finishing a longitudinally curved tooth tapered gearwhich comprises employing a tool of tapered gear form that haslongitudinally curved teeth whose side surfaces are conical and that hasthe sides of its teeth grooved longitudinally to provide cutting edgeswhich extend longitudinally of the teeth parallel to the root lines ofthe teeth on both sides of the teeth, positioning said tool inengagement with the work so that the axis of the tool is angularlydisposed to and intersects the axis of the work,-and rotating the tooland work in engagement while eflecting a relative depthwise move:

ment between the tool and work to finish the teeth of the gear to thedesired depth.

5. The method of finishing a longitudinally curved tooth tapered gearwhich comprises em ploying a tool of tapered gear form that haslongitudinally curved teeth and that has cutting edges formed in thesides of its teeth by alternate grooves and lands that extendlongitudinally of its teeth parallel to the root lines of the teeth, andwhich has wider lands on the coast sides of its teeth than on the drivesides thereof, positioning said tool in engagement with the gear so thatthe axis of the tool is angularly disposed to and intersects the axis ofthe gear, and rotating the tool in engagement with the gear whileeffecting a relative depthwise movement between the tool and gear tofinish the teeth of the gear to the desired depth.

6. The method of finishing one member of a pair of longitudinally curvedtooth hypoid gears which comprises employing a tool of tapered gear formthat has longitudinally curved teeth whose opposite sides have differentpressure angles and have cutting edges formed on both sides thereof thatextend longitudinally of the teeth parallel to the root lines of theteeth, positioning said tool in engagement with the gear so that theaxis of the tool is angularly disposed to the axis of the gear andofiset from the axis of the gear the same distance as the offset betweenthe axes of the pair of gears when in mesh, and rotating the tool inengagement with the gear while effecting a relative depthwise movementbetween the tool and gear to finish the teeth of the gear to the desireddepth. 7

7. The method of finishing a longitudinally curved tooth tapered gearwhich comprises employing a tool of tapered gear form that haslongitudinally curved teeth whose opposite sides have different radii ofcurvature from the mating sides of the gear to be finished and are socurved longitudinally that they contact with the tooth surfaces of thegear to be finished midway the length of said tooth surfaces, androtating said tool in engagement with the gear while producing arelative movement between the tool and gear longitudinally of the teethof the gear, and effecting a relative depthwise movement between thetool and gear to finish the teeth of the gear to the desired depth.

8. The method of finishing a longitudinally curved tooth tapered gearwhich comprises employing a tool of tapered gear form that haslongitudinally curved teeth whose opposite sides have radii of curvaturedifferent from the mating sides of the gear to be finished and are socurved longitudinally that they will contact with the tooth surfaces ofthe gear midway of the length of said tooth surfaces, and positioningsaid tool in engagement with the gear so that the axis of the tool isangularly disposed to and intersects the axis of the gear, and rotatingsaid tool and gear in engagement while producing a relative movementbetween the tool and gear about an axis ofiset from but parallel to theaxis of the gear, and effecting a depthwise movement between the tooland gear to finish the teeth of the gear to the desired depth.

9. The method of finishing a longitudinally curved tooth tapered gearwhich comprises employing a tool of tapered gear form that haslongitudinally curved teeth whose opposite sides have the same radii ofcurvature as the meshing tooth surfaces of the gear to be finished andare grooved to form cutting edges which extend longitudinally of theteeth and are equally inclined on opposite sides of the teeth to thepitch line of said tool, and rotating the tool in engagement with thegear while effecting a relative depth wise movement between the tool andgear to finish the gear to the desired depth.

10. The method of finishing a longitudinally curved tooth tapered gearwhich comprises employing a tool of tapered gear form that haslongitudinally curved teeth whose opposite sides have radii of curvaturedifferent from the mating sides of the gear to be finished and are socurved longitudinally that they contact with the tooth surfaces of thegear midway of the length of said teeth, and are grooved to form cuttingedges which extend longitudinally of the teeth and which are inclined tothe lines of contact between said teeth and the mating tooth surfaces ofthe gear to be shaved, and rotating said tool in engagement with thegear while producing a relative movement between the tool and gear aboutan axis offset from but parallel to the axis of the gear, and effectinga depthwise movement between the tool and gear to finish the teeth ofthe gear to the desired depth.

11. The method of finishing a longitudinally curved tooth bevel gearwhich comprises employing a tool of tapered gear form that haslongitudinally curved teeth whose opposite sides have radii of curvaturediiferent from the mating sides of the gear to be finished and are socurved longitudinally that they will contact with the tooth surfaces ofthe gear midway of the length of said tooth surfaces, and are grooved toform cutting edges which extend longitudinally of the teeth and whichare inclined to the lines of contact between said teeth and the toothsurfaces of the gear to be finished when the tool and gear are rotatedin mesh, and positioning said tool in engagement with the gear so thatthe axis of the tool is angularly disposed to and intersects the axis ofthe gear, and rotating the tool and gear in engagement while roducing arelative movement between the tool and gear longitudinally of the teethof the gear, and effecting a relative depthwise movement between thetool and gear to finish the teeth of the gear to the desired depth.

12. The method of finishing a bevel gear which comprises employing atool of tapered gear form that has its pitch surface inclined at otherthan 180 to its axis and which has teeth of straight profile and thathas cutting edges formed on both sides of its teeth which extendlongitudinally of the teeth, all of which are inclined at equal anglesto the lines of contact between the opposite sides of the teeth and themating tooth surfaces of the gear to be finished when the tool and gearare rotated in mesh, and positioning said tool in engagement with thegear with the axis of the tool intersecting the axis of the gear andangularly disposed thereto, and rotating the tool and gear in engagementwhile effecting a relative depthwise movement between the tool and gearto finish the teeth of the gear to the desired depth.

13. The method of shaving a longitudinally curved tooth tapered gearwhich comprises employing a tool of tapered gear form which has itspitch surface inclined to its axis at other than and which haslongitudinally curved teeth whose sides are conical and have radii ofcurvature different from the ridii of curvature of the sides of theteeth of the gear to be shaved and which has cutting edges formed onboth sides of its teeth that are inclined to the lines of contactbetween said teeth and the teeth of the gear to be finished when thetool gear are retated in mesh, and rotating said tool in engagement withthe gear while producing a relative movement between the tool and gearlengthwise of the teeth of the gear, and effecting a relative movementbetween the tool and gear depthwise of said teeth.

14. The method of finishing a bevel gear which comprises employing atool of tapered gear form that has radially arranged teeth which havecutting edges formed on their opposite sides that extend longitudinallyof the teeth and that are inclined to both the top and root lines of theteeth, positioning said tool in engagement with the gear so that theaxis of the tool is angularly disposed to and intersects the axis of thegear, and rotating the tool and gear in mesh while effecting a relativedepthwise movement between the tool and gear to finish the teeth of thegear to the desired depth.

15. The method of finishing one member of a pair of longitudinallycurved tooth tapered gears which comprises employing a tool of taperedgear form that has longitudinally curved teeth whose oppositesides areconical and have cutting edges formed thereon that extend longitudinallyof the teeth and that are inclined to the lines of contact between saidteeth and the teeth of the gear to be finished when the tool and gearare rotated in mesh, positioning the tool in engagement with the gear sothat the tool and gear axes have the same relative positions as the axesof the gear being finished and its mate when the pair are in mesh, androtating the tool and gear in engagement while effecting a relativedepthwise feed movement between the tool and gear to finish the teeth ofthe gear to the desired depth.

16. The method of finishing one member of a pair of longitudinallycurved tooth tapered gears which comprises employing a tool of taperedgear form which has its pitch surface inclined to its axis at other than180 and which has longitudinally curved teeth whose sides are conicaland which has cutting edges formed on both sides of its teeth byalternate grooves and lands that extend longitudinally of the teethparallel to the root lines of the teeth, and which has wider lands onthe longitudinally concave sides of its teeth than on the longitudinallyconvex sides thereof, positioning said tool and gear in engagement sothat the axes of tool and gear have the same relative positions as theaxes of the gear and its mate when the pair are in mesh, and rotatingsaid tool in engagement with the gear while effecting a relativedepthwise movement between the tool and gear to finish the teeth of thegear to the desired depth.

WINFRED A. l/VI'IHAM.

